With the scaling down of semiconductor devices, new materials with high dielectric constant are required. Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) have become the main deposition techniques for such thin films since CVD and ALD may provide different films (metal, oxide, nitride, etc.) having a finely defined thickness and high step coverage. In CVD and ALD, the precursor molecule plays a critical role to obtain high quality films with high conformality and low impurities.
Among high-k dielectrics, Group 4 based materials, such as Group 4 oxides TiO2, HfO2 or ZrO2, are very promising, whether used as pure or mixed oxides or in laminates. In addition, Group 4 metal-containing films, such as TiN, may be used for electrode and/or Cu diffusion barrier applications. The Group 4 oxides may also be used for their etch resistance properties in lithography applications, such as for hard masks or spacer-defined multiple patterning applications.
Cyclopentadienyl (Cp) bridged Group 4 metal compounds have been used as precursors for CVD and/or ALD of Group 4 metal-containing films. For example, U.S. Pat. No. 8,946,096 to Ahn et al. discloses group 4 metalorganic compounds utilized in CVD or ALD having the formula
wherein M is Ti, Zr or Hf, R1 is C1 to C4 alkyl, R2 and R3 are independently C1 to C6 alkyl. US 2015/0255276 to Cho et al. discloses an organometallic precursor, used as a deposition source in CVD and ALD processes, represented by a chemical formula of Xn(M)(R1)m(R2)k, wherein M is Ti, Zr or Hf. X is a ligand of M and one of 6,6-dimethylfulvenyl, indenyl, cyclopentadienyl and cyclopentadienyl substituted with an amino group. R1 and R2 are ligands of M, and each independently an amino group or an ethylenediamino group. Each n, m and k is a positive integer, and n+m+k=3 or 4. KR10-2014-0078534 to Castle et al. discloses metal precursors and metal-containing thin film prepared with the metal precursors including Group 4 complexes having the structure formula:
wherein M is selected from the group consisting of Zr, Hf and Ti, Xa and Xb are each independently NRaRb or ORc, Xc is (NRd) or O, Ra to Rd are each independently a hydrogen atom or a C1 to C5 alkyl group, R are each independently a hydrogen atom or a C1 to C5 alkyl group, and m is an integer of 0 to 4. Kang et al. disclose forming TiO2 thin films using (CpN)Ti(NMe2)2 and oxygen remote plasma (Kang et al., “Growth behavior and structural characteristics of TiO2 thin films using (CpN)Ti(NMe2)2 and oxygen remote Plasma”, Phys. Status Solidi A, 2014, 212, No. 3, p 674-679).
Some Cp bridged Group 4 metal compounds are synthesized and used for catalysts or other purposes. For example, J Okuda discloses metalorganic catalysts having linked amido-cyclopentadienyl ligands such as Ti(R-Cp-SiMe2-NR—)(NR2)2 (J Okuda, “Linked Amido-Cyclopentadienyl Complexes of Group 3 and 4 Metals: The First “Post-Metallocenes” Metalorganic Catalysts for Synthesis and Polymerization, pp 200-211, 1999). Herrmann et al. disclose Cp(CH2CH2—O—)Zr(NMe2)2 prepared as potential catalysts (Herrmann et al., “Doubly Bridged vac-Metallocenes of Zirconium and Hafnium”, Angewandte. Chem. Int. Ed. Eng, 1994, 33(19), p 1946-1949). Kim et al. disclose synthesis of (Me4Cp-CH2—NtBu)Zr(NEt2)2 and (1,3-Me2C5H2—CHPh-NtBu-κN)Zr(NMe2)2 (Kim et al., “sp3-C1-Bridged 1,3-Me2Cp/Amido Titanium and Zirconium Complexes and Their Reactivities towards Ethylene Polymerization”, Eur. J. Inorg. Chem. 2004, p 1522-1529). Jesus Cano and Klaus Kunz disclose syntheses of some P, C, Si contained Cp-amino bridged compounds (Jesus Cano, Klaus Kunz, “How to synthesize a constrained geometry catalyst (CGC)—A survey”, Journal of Organometallic Chemistry 692, 2007, p 4411-4423). Syntheses of carbon-bridged cyclopentadienyl amido Group 4 metal complexes were reported in Piet-Jan Sinnema's PhD dissertation in 1999 (Piet-Jan Sinnema, “Carbon-Bridged Cyclopentadienyl Amido Group 4 Metal Complexes”, University of Groningen, 1999).
Accordingly, those skilled in the art continue to seek highly thermally stable, Group 4 compounds suitable for vapor phase thin film deposition with controlled thickness and composition at high temperature.